• Title/Summary/Keyword: High-tensile steel plates

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Modified Design Formula for Predicting the Ultimate Strength of High-tensile Steel Thin Plates

  • Park, Joo Shin;Seo, Jung Kwan
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.27 no.3
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    • pp.447-456
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    • 2021
  • Methods for predicting the ultimate/buckling strength of ship structures have been extensively improved in terms of design formulas and analytical solutions. In recent years, the design strategy of ships and offshore structures has tended to emphasize lighter builds and improve operational safety. Therefore, the corresponding geometrical changes in design necessitate the use of high-tensile steel and thin plates. However, the existing design formulas were mainly developed for thick plates and mild steels. Therefore, the calculation methods require appropriate modification for new designs beased on high-tensile steel and thin plates. In this study, a modified formula was developed to predict the ultimate strength of thin steel plates subjected to compressive and shear loads. Based on the numerical results, the effects of the yield stress, slenderness ratio, and loading condition on the buckling/ultimate strength of steel plates were examined, and a newly modified double-beta parameter formula was developed. The results were used to derive and modify existing closed-form expressions and empirical formulas to predict the ultimate strength of thin-walled steel structures.

Ultimate Compressive Strength Analysis of TMCP High Tensile Steel Plates with HAZ Softening(2nd Report) (HAZ 연화부를 가진 TMCP형 고장력강판의 압축최종강도에 관한 연구 - 제 2 보)

  • 백점기;고재용
    • Journal of Welding and Joining
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    • v.9 no.2
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    • pp.44-50
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    • 1991
  • The use of high tensile steel plates is increasing in the fabrication of ship and offshore structures. The softening region which has lower yield stress than base metal is located to prevent cracking in the conventional high tensile steel. Also, thermo mechanical control process(TMCP) steel with low carbon equivalent has the softening region which occurs in the heat affected zone when high heat input weld is carried out. The softening region in the high tensile steel gives rise to serious effect on structural strength such as tensile strength, fatigue strength and ultimate strength. In order to make a reliable structural design using high tensile steel plates, the influence of the softening on plate strength should be evaluated in advance. In the previous paper, the authors discussed the ultimate compressive strength of 50HT steel square plates with softening region. In this paper, the ultimate compressive strength with varying the yield stress of softening region and the aspect ratio of the plate is investigated by using the elasto-plastic large deformation finite element method.

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A Study on the Materials Characteristics of High Tensile Strength Steel(SM570) Plates (고장력(SM570)강재의 재료특성에 관한 연구)

  • Im, Sung Woo;Ko, Sang Ki;Ha, Dong Woo;Oh, Sang Hoon;Chang, In Hwa
    • Journal of Korean Society of Steel Construction
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    • v.12 no.6
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    • pp.649-659
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    • 2000
  • In this study, the chemical compositions and mechanical properties of high tensile strength steel plates in accordance with their thickness are quantitatively estimated, that are steel plates SM570 to be purposed to use in building structure. Test results of steel plates SM570 are compared with those of steel plates SS400 and steel plates SM490 mostly using building structure. It is found that chemical compositions, carbon equivalent, parameter of welding crack susceptibility, yield strength, tensile strength, elongation, and impact strength have satisfied the prescribed value in KS code for all case of thickness.

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A Study on the Large Deflection Behavior of Ship Plate with Secondary Buckling (2차좌굴을 포함하는 선체판의 대변형거동에 관한 연구)

  • 고재용
    • Journal of Advanced Marine Engineering and Technology
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    • v.23 no.4
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    • pp.565-573
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    • 1999
  • Hihg Tensile Steel enables to reduce the plate thickness comparing to the case when Mild Steel is used. From the economical view points this is very preferable since the reduction in the hull weight. however to use the High Tensile Steel effectively the plate thickness may become thin so that the occurrence of buckling is inevitable and design allowing plate buckling may be necessary. If the inplane stiffness of the plating decreases due to buckling the flexural rigidity of the cross sect6ion of a ship's hull also decreases. This may lead to excessive deflection of the hull girder under longitudinal bending. In these cases a precise estimation of plate's behavior after buckling is necessary and nonliner analysis of isolated and stiffened plates is required for structural sys-tem analysis. In this connection this paper discusses nonlinear behaviour of thin plate under thrust. Based on the analytical method elastic large deflection analysis of isolated plate is perform and simple expression are derived to evaluated the inplane rigidity of plates subjected to uniaxial compression.

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A Study on the Secondary Buckling Behavior of Ship Plate (선체판부재의 2차좌굴거동에 관한 연구)

  • 고재용
    • Journal of the Korean Institute of Navigation
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    • v.20 no.1
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    • pp.47-58
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    • 1996
  • The use of high tensile steel plates is increasing in the fabrication of ship and offshore structures. The main portion of ship structure is usually composed of stiffened plates. In these structures, plate buckling is one of the most important design criteria and buckling load may usually be obtained as an eigenvalue solution of the governing equations for the plate. To use the high tensile steel plate effectively, its thickness may become thin so that the occurrence of buckling is inevitable and design allowing plate buckling may be necessary. When the panel elastic buckling is allowed, it is necessary to get precise understandings about the post-buckling behaviour of thin plates. It is well known that a thin flat plate undergoes secondary buckling after initial buckling took place and the deflection of the initial buckling mode was developed. From this point of view, this paper discusses the post-buckling behaviour of thin plates under thrust including the secondary buckling phenomenon. Series of elastic large deflection analyses were performed on rectangular plates with aspect ratio 3.6 using the analytical method and the FEM.

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Slip Coefficients between Steel Plates Fixed with High Tension Bolts (고장력볼트로 체결되는 철판 사이의 미끄럼계수)

  • Kim, Choong-Hyun
    • Tribology and Lubricants
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    • v.24 no.6
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    • pp.338-342
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    • 2008
  • Tensile test results using three kinds of steel structure specimens are measured and compared. Slip coefficient between shot blasted steel plates was greater than 0.6. For the case of the plates coated with Super zinc, it revealed that the coefficients were greater than 0.5. On the other hand, Super epoxy coating decreased its slip coefficient less than 0.25. Steel plates coated with Super zinc are proved to be practically applicable to the steel structures with anti-corrosion characteristics and clean surfaces.

A Study on the Nonlinear Behavior of Plate under Thrust (면내압축하중을 받는 선체판의 비선형거동에 관한 연구)

  • 고재용
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 1996.09a
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    • pp.95-110
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    • 1996
  • High Tensile Steel enables to reduce the plate thickness comparing to the case when Mild Steel is used. From the economical view point this is very preferable since the reduction in the hull weight. However to use the High Tensile Steel effectively the plate thickness may become thin so that the occurrence of buckling is inevitable and design allowing plate buckling may be necessary. If the inplane stiffness of the plating decreases due to buckling, buckling may be necessary. If the inplane stiffness of the plating decreases due to buckling the flexural rigidity of the cross section of a ship's hull also decreases. this may lead to excessive deflection of the hull girder under longitudinal bending. In these cases a precise estimation of plate's behavior after buckling is necessary and nonlinear analysis of isolated and stiffened plates is required for structural system analysis. In this connection this paper discusses nonlinear behaviour of thin plate under thrust. Based on the analytical method elastic large deflection analysis of isolated plate is perform and simple expression are derived to evaluate the inplane rigidity of plates subjected to uniaxial compression.

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Tensile strength of thick plate welded joint with weld HAZ softening for hight heat input welding (대입열 용접에 의한 HAZ연화부를 갖는 극후판 용접이음부의 인장강도 평가)

  • Jang Tae-Won;Nam Seong-Gil;An Gyu-Baek
    • Proceedings of the KWS Conference
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    • 2006.05a
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    • pp.92-93
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    • 2006
  • In recent time there are vigorous requirement for the use of thick steel plate in various industrial fields including shipbuilding industry. Application of TMCP steel plates, especially, is increase progressively. As a welding process for thick steel plate assembly high heat input welding method is used. However, HAZ softening of TMCP steel plates has a possibility to reduce the strength of welded joint. In this study, therefore, tensile strength of TMCP welds had softened HAZ was examined using numerical calculation and experiment.

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Effect of Chemical Compositions on Microstructure and Mechanical Properties of Base Metal and HAZ of Bainitic Steel Plates (베이나이트계 후판강의 모재 및 열영향부의 미세조직과 기계적 특성에 미치는 화학 조성의 영향)

  • Cho, Sung Kyu;Joo, Hyung Goun;Shin, Sang Yong
    • Korean Journal of Materials Research
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    • v.29 no.4
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    • pp.211-220
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    • 2019
  • In this study, three kinds of bainitic steel plates are manufactured by varying the chemical compositions and their microstructures are analyzed. Tensile and Charpy impact tests are performed at room and low temperature to investigate the correlation between microstructure and mechanical properties. In addition, heat affected zone (HAZ) specimens are fabricated by a simulation of welding processes, and the HAZ microstructure is analyzed. The base steel that has the lowest carbon equivalent has the highest volume fraction of acicular ferrite and the lowest volume fraction of secondary phases, so the strength is the lowest and the elongation is the highest. The Mo steel has a higher volume fraction of granular bainite and more secondary phases than the base steel, so the strength is high and the elongation is low. The CrNi steel has the highest volume fraction of the secondary phases, so the strength is the highest and elongation is the lowest. The tensile properties of the steels, namely, strength and elongation, have a linear correlation with the volume fraction of secondary phases. The Mo steel has the lowest Charpy impact energy at $-80^{\circ}C$ because of coarse granular bainite. In the Base-HAZ and Mo-HAZ specimens, the hardness increases as the volume fraction of martensite-austenite constituents increases. In the CrNi-HAZ specimen, however, hardness increases as the volume fraction of martensite and bainitic ferrite increases.

Square CFST columns under cyclic load and acid rain attack: Experiments

  • Yuan, Fang;Chen, Mengcheng;Huang, Hong
    • Steel and Composite Structures
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    • v.30 no.2
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    • pp.171-183
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    • 2019
  • As China's infrastructure continues to grow, concrete filled steel tubular (CFST) structures are attracting increasing interest for use in engineering applications in earthquake prone regions owing to their high section modulus, high strength, and good seismic performance. However, in a corrosive environment, the seismic resistance of the CFST columns may be affected to a certain extent. This study attempts to investigate the mechanical behaviours of square CFST members under both a cyclic load and an acid rain attack. First, the tensile mechanical properties of steel plates with various corrosion rates were tested. Second, a total of 12 columns with different corrosion rates were subjected to a reversed cyclic load and tested. Third, comparisons between the test results and the predicted ultimate strength by using four existing codes were carried out. It was found that the corrosion leads to an evident decrease in yield strength, elastic modulus, and tensile strain capacity of steel plates, and also to a noticeable deterioration in the ultimate strength, ductility, and energy dissipation of the CFST members. A larger axial force ratio leads to a more significant resulting deterioration of the seismic behaviour of the columns. In addition, the losses of both thickness and yield strength of an outer steel tube caused by corrosion should be taken into account when predicting the ultimate strength of corroded CFST columns.